When you go to buy a Light Bulb, the Higher the Watts, the Brighter the Bulb, Right. And a Brighter Bulb means its running Hotter.
This is Basicaly what is going on with a Carto or Atty.
Watts are calculated by taking the Voltage (Volts) Squared and then Dividing it by the Resistance (Ohms).
Watts = (Volts x Volts) / Ohms
If the Volts remain the same, the only way to make the Watts go Up or Down is to Change the Ohms.
Since the Ohms are on the Bottom of the Fraction, (Volts x Volts) / Ohms, making the Ohms Smaller makes the Watts Bigger. And when the Ohms are made Larger, they go into the top of the , (Volts x Volts) / Ohms, less times, Hence the Watts are Less.
So just remember that if you Lower the Ohms of what you are using right now, say from 2.8 ohms to 2.4 ohms, the result will be the Carto/Atty Runs Hotter. Raise the Ohms and the Carto/Atty runs Cooler. A Carto or Atty that runs Hotter will make More Vapor. And it will make More Flavor to a Point. But if it runs Too Hot, then you e-Liquids start to taste Burnt.
Most people Experiment by buying Cartos/Attys of Lower and Lower Ohms until they Reach the Point where there e-Liquids taste Burnt. There is no Rule that fits Everyone as to what Ohms are Right. It's all based on what the Individual Likes and what their e-Liquids can Handle.